China plans to build a series of hydroelectric power dams on one of the country's last free-flowing rivers. Officials say the project on the Nu River is necessary to provide much needed investment and electricity to an impoverished region. But environmentalists and international organizations fear the dams will harm the river valley's unique environment.

The Nu River winds through China's southwest Yunnan Province along the border with Burma and Tibet.

The U.N. Educational, Scientific and Cultural Organization designated parts of the river area a World Heritage site in 2003.

The U.N. agency says the area is China's last stronghold for rare and endangered plants and animals and is perhaps the most biologically diverse temperate region on earth.

But there are concerns that a plan to build up to 13 hydroelectric power dams on the river may harm the unique environment.

David Sheppard is head of the Protected Areas Program at the World Conservation Union, the organization that evaluates and monitors World Heritage sites for UNESCO, says the dams could place the World Heritage site in danger.

"These impacts could be direct, such as impacts on water quality, water flow, impacts on fisheries and other aquatic species. They could be indirect in terms of issues such as road construction and dam construction and people moving into the area that could impact on the natural values of the site," said Sheppard.

Chinese law requires the government to notify the public about large construction projects and the likely effect on the environment. But people who live along the Nu River say they have been kept in the dark about the plans. The project was delayed in 2004 until an environmental study could be done, but the report has yet to be released.

Li Zhihua lives in Xiaoshaba village. Government plans call for one of the dams to be built here and for hundreds of villagers to be moved. Li says he heard in February that the government was going to build the dam, but the villagers have received no official notice.

"Even though they are cadres they cannot just tell us where we should move to without discussing with us. Although we support the government's project, the construction of the dam should comply with the law and they should meet the people's demands when it comes to resettlement," said Le.

Downstream in Burma and Thailand, environmental organizations also want more information from the Chinese government.

Witoon Permpongsacharoen works for a group in Thailand called Towards Ecological Recovery and Alliance.

He says a dam on the upper part of the Mekong in China has caused soil erosion downstream in Thailand and Laos and blocked fish migration. He does not want to see the same thing happen downstream on the Nu River.

"We would like to see the process of planning and decision more collective with the other downstream country. And also, we would like to see a study of the impact, both environmental and social impact, not just a local area but, looking the accumulative impact for the whole basin," said Witoon Permpongsacharoen.

Environmentalists say Chinese officials often put economic growth ahead of environmental protection and the country in recent years has suffered from increasing pollution due to industrial growth.

"If the effect on the environment is very severe, the Chinese government will take due measures to protect the environment," he said. "If the river is cross-border, we will also take into consideration the interests of people in downstream countries. We are not willing to do things that will harm their interests."

Chinese officials say if all 13 dams are built they will produce more clean energy than the Three Gorges Dam, the world's largest hydroelectric power project. The 20,000 megawatts of electricity from the dams will help feed the country's growing energy needs.

Despite the concerns, the project looks set to go ahead. On the Nu River, workers drill holes in rock cliffs and the riverbed. They are taking geological samples to determine the best locations for the dams.

Local officials say the dams will attract billions of dollars in investment that will improve the local infrastructure and create jobs in this remote and impoverished region.

Chinese news media report that half of the Nu River residents live below China's poverty line, and their average salary is $120, about a third of the national average for farmers. Chinese experts say one in three people in the area have never used electricity.

Environmental activists doubt that local people will see many benefits. They say among other problems, the best land in the Nu valley is along the river, and so will be flooded by the dams. The farmers will wind up on mountainsides, where the soil is poor.

Many villagers along the river support the dam project. But they worry that local officials will not compensate them fairly or move them to good land.

The central government acknowledges that in many cases when land has been taken for development projects, local authorities embezzled much of the compensation money that was to go to farmers.

Premier Wen Jiabao earlier this year vowed the government would protect farmers who are relocated.

"We must give adequate and due compensation to farmers whose lands are seized," he said. "And, we believe land transfer revenues should be mainly paid to farmers affected."

Recent Chinese media reports indicate three or four dams will be built in the first phase of construction. But there is still no confirmation of the plan from the government and no information about when construction will begin or where.

UNESCO and the World Conservation Union are sending a team to the area to investigate potential damage to the World Heritage site if dam construction goes ahead as planned.